Should you be faced with the horrors of a shaken can of beer and an urgent need to open it, science has solved the question of whether or not tapping the can helps reduce the fizz when it is opened.
Researchers from the University of Southern Denmark carried out a randomised controlled trial of 1,000 cans of beer (PDF). The cans were either shaken and not tapped, or shaken and tapped, or not shaken and tapped or indeed not shaken and not tapped. Clear?
The cans were then opened and weighed to see how much precious beverage was lost.
As the paper's summary notes: "Preventing or minimising beer loss when opening a can of beer is socially and economically desirable." That, we can all surely agree, is true.
The summary continues: "One theoretically grounded approach is tapping the can prior to opening, although this has never been rigorously evaluated."
In order to fill this gaping hole in human understanding, the boffins procured 1,000 330ml cans of Carlsberg.
Cans selected for abuse were shaken for two minutes and then tapped "three times with a single finger".
Controversially, the cans were tapped on the side when every Brit in a hurry knows that the can should be tapped on the top.
The researchers told us: "We too are more familiar with the top-tap approach. However, we adapted our method for this study based on a theoretical physics article. This article theorised that the loss of liquid was due to bubbles that form on the sides of the can during shaking, dragging liquid with them as they expand, dislodge from the wall and rise once the can is opened and pressure is released."
After the researchers performed the top-tap, the cans were then weighed before and after opening, and paper towels used to absorb the resulting mess.
The mass of the cans, to +/-0.1 grams, showed no significant statistical difference whether the can was tapped or not – there was a mean difference of -0.159 grams of beer lost when the can was tapped.
So the researchers conclude some what gloomily: "Thus, the practice of tapping a beer prior to opening is unsupported. The only apparent remedy to avoid liquid loss is to wait for bubbles to settle before opening the can."
The research team was led by Dr Elizaveta Sopina, who otherwise seems to waste her time researching the effectiveness of different interventions for Alzheimer's disease and advanced dementia.
The team told us Carlsberg donated over 1,000 330mL cans of its own-brand pilsner style beer to the PhD Association "so that we may undertake this study". Ahem.
The researchers "reserved a few of the opened cans from the exercise for our own consumption at the end of data collection". They gave the rest away to thirsty uni students and staff "at the end of a hot Friday". ®